Cyclic ethers-based solid electrolyte derived from in situ ring-opening polymerization strategy

Although solid-state polymer electrolytes (SPEs) are expected to solve the safety hazards and limited energy density in the energy storage systems, they still encounter an inferior electrode/electrolyte interface when prepared in an ex situ manner. Recently, in situ polymerization of SPEs favor high interfacial infiltrability, improved interface contact, and reduced interface resistance, owing to the formation of a "super-conformal" interface between electrode and electrolyte. Especially, in situ strategies employing ring-opening polymerization (ROP) are emerging as dazzling stars, further enabling moderate polymerization conditions, controllable molecular structure, and reduced interfacial side reaction. As the main monomers that can be in situ polymerized via the ROP strategy, cyclic ethers have been used to construct the CE-SPEs with many merits, including good battery electrochemical performances and a simple assembly process. Here, as a systematic summarization of the existing reports, this review focuses on the polymerization mechanism of ROP, the design principles of CE-SPEs electrolytes, and the recent application of in situ CE-SPEs. In particular, this review thoroughly discusses the selection of different cyclic monomers, initiators and various modification approaches in in situ fabricating CE-SPEs. Ending with offering future challenges and perspectives, this review envisions shedding light on the profound understanding and scientific guidance for further development of high-performance in situ CE-SPEs. The superiority of in situ polymerization and the scheme of in situ ROP reaction. • In situ polymerization of SPEs exhibits remarkable performance in solid state lithium-based batteries. • This review summarizes the in situ polymerization methods to fabricate CE-SPEs. • In situ ring-opening polymerization strategy provides further insights into the design of high performance SPEs.